The desire, as well as the need, to calculate ever more accurate values of π, the ratio of the circumference of a circle to its diameter, has challenged mathematicians for many centuries. In recent years, π computations have provided some fascinating examples of computational mathematics. But ﬁrst, a little historical background, which we have condensed from a 1997 article . Additional historical details are available from the fascinating new book Pi Unleashed , and from [49, 74]. We should also mention the MacTutor web site, maintained by the Department of Mathematics at the University of St. Andrews in Scotland: http://www-gap.dcs.st-and .ac.uk/∼history. This is particularly good for biographical information about historical mathematicians, including those involved with π.